Question

which variable is directly proportional to frequency?
velocity
wavelength
position
energy

Explanation:

The energy \(E\) of a photon is given by the formula \(E = h
u\), where \(h\) is Planck's constant and \(
u\) is the frequency. This shows a direct proportionality (\(E\propto
u\)).
For velocity (\(v=\lambda
u\) in a vacuum \(v = c\) (constant), so \(v\) is not directly proportional to \(
u\) when \(v\) is constant).
Wavelength \(\lambda=\frac{v}{
u}\) (in a medium with constant \(v\)), so \(\lambda\) is inversely proportional to \(
u\).
Position has no direct proportionality relation with frequency from basic wave - related equations.

Answer:

energy